Satellite Navigation Systems for Land Vehicles

Today's motorists often must confirm their route by referring to a roadmap. Looking at a map while driving creates a poor traffic situation, one even more acute for drivers of emergency service vehicles. To address this problem, development engineers at the General Motors Technical Cener and Delco Electronics integrated an experimental GPS receiver into a GM Buick Park Avenue. The receiver is designed to acquire and sequentially track signals from four satellites. The vehicle's precise latitude, longitude, and altitude are determined and presented on a color cathode ray tube (CRT) map display in the car's instrument panel.     

Geostationary Satellite Navigation Systems

The concept of position determination using geostationary satellites as an alternative to the global positioning system (GPS) is studied. The advantage of a geostationary system is that only three, or at most four, satellites are required to cover the continental United States. A total of twelve satellites are sufficient for global coverage (excluding polar regions), or eight if only longitude and latitude, but not altitude, are measured. The system involves the determination of the range to either four geostationary satellites or, if the altitude is not measured, three geostationary satellites. The accuracy of the proposed systems are evaluated to obtain the rms error associated with position determination, and the concept for the implementation of measurements required by the systems is presented. The accuracy of the systems are adequate for civilian use in the continental United States; however, there is a degradation in accuracy as the location of the user approaches the equator.     

A Closed-Form Solution for Doppler Satellite Navigation

Doppler satellite navigation relies on an initial position estimate with an iterative solution. A closed-form solution of this problem, which forms the basis of a complete analytic treatment, is presented. The solution is exact for arbitrary satellite orbits with an ellipsoid Earth model.     

跟飞编队卫星相对导航自适应EKF算法研究

针对跟踪星对目标星跟飞编队的相对导航问题,提出了基于自适应扩展卡尔曼滤波（EKF）的相对导航算法。以线性离散化的椭圆参考轨道相对动力学模型为导航状态方程．设计了虚拟测量量及相应的测量矩阵,避免了求解雅可比矩阵的复杂计算。为了适应构型尺寸变化引起的模型误差变化,提出了模型误差在线估计算法。仿真显示,算法具有较快的收敛速度和较高的估计精度。该研究成果可作为卫星编队应用的有益参考。     

Everyman's Doppler Satellite Navigation System

This paper describes a system of navigation by measurement of the Doppler shift in the radio transmissions from a near-Earth satellite, and simple equipment for making the measurements. It also shows that the current information which is needed by the navigator can be reduced to a number containing six decimal digits. Finally, it shows that the computations needed for the navigator to obtain a fix can be performed witlh the aid of tables that can be prepared at least 18 months in advance. Using these tables and a simple slide rule, but no other computational aids, a fix accurate to about 500 meters can be obtained in about 10 minutes. More accuracy can be obtained at the expense of time, or time can be saved at the expense of accuracy.     

卫星导航系统发展动态

卫星导航系统是20世纪60年代中期发展起来的一种新型导航系统,90年代,卫星导航时入全运行和盛行时期,除了用于陆上,海上和空中的航行引导外,几乎扩展到军事和经济的各个方面,目前,除了已经运行的美国的GPS（全球定位系统）和俄罗斯的GLONASS（全球导航卫星系统）外,欧盟也正在积极开发伽利略系统。本文分别介绍GPS、GLONASS和伽利略系统的发展状况。     

导航卫星的短弧运动学定轨

导航卫星在姿轨控和轨道恢复期间,由于观测数据有限,传统的统计定轨理论难以实现导航卫星精密定轨。本文尝试采用一种不依赖轨道动力学的、新的运动学定轨方法来处理短弧和复杂动力学过程中的定轨,提出了基于多项式拟合的短弧运动学定轨算法,并提出2种不同的实现方案。该算法充分利用了高采样率的测轨数据,减少了结果的噪声,其优点在于不需要长时间累积测轨数据,可以实现近实时快速计算,克服了动力学法定轨发散和单点定位无法获得卫星速度信息等不足。对COMPASS M-01导航卫星实测数据的处理表明,10min左右短弧运动学定轨的位置精度可以优于10m,速度精度优于4cm/s,满足了短弧跟踪条件下RDSS对卫星轨道精度的要求,实现了短弧跟踪条件下卫星精密定轨,但从轨道预报精度来看,该方法仅仅适用于短期预报。     

未来的GPS-Galileo组合导航卫星系统

随着卫星导航定位技术的发展,用户对卫星导航系统提供的服务性能提出了更高的要求,希望能得到高精度、高可靠性、高动态实时的导航定位服务。而目前存在的卫星导航系统已逐渐不能满足这些需求,如果GPS-Galileo组合系统能够很好兼容,则是一个很好的解决途径。     

Selective Combinations in Personal Satellite Navigation

Methods for selecting satellite combinations in personal satellite navigation are presented and categorized. The methods include different algorithms and various data parameters and computed parameters. This paper offers a summary on the topic as well as future considerations     

卫星导航定位方程的病态条件

定位精度因子(PDOP)上限取值是导航星座设计及其性能评价的基本依据。本文系统地论述卫星导航定位方程及其精度评定算法以及线性方程病态条件,通过实测和仿真数值试验结果对比分析,详细论证PDOP与卫星导航定位方程病态条件的关系,进而确定PDOP上限取值,以满足实际工程应用需求。     

Observability of Relative Navigation Using Range-Only Measurements

A simulation tool is described which is capable of determining the observability of various fleet configurations and maneuvers in a relative navigation environment. The motion of the relative grid established by the navigation controller is explicitly modeled as a function of the errors in his dead-reckoning sensors. The simulation uses centralized, optimal processing of an extended Kalman filter. Results show observability on a good geometry, with some degradation in performance when dead-reckoning sensor errors change rapidly.     

全球卫星导航系统兼容性分析方法研究

根据全球卫星导航系统信号捕获、载波跟踪和数据解调的原理,优化了等效载波功率与噪声密度比模型.针对有多普勒频率时的情况,提出了C/A码自干扰时的捕获-频谱隔离系数.结果显示,随着多普勒频率的变化,频谱隔离系数有着明显的变化.通过对仿真结果的分析,验证了模型的有效性,也为后续卫星导航信号的优化设计提供了支持.     

Navy Navigation Satellite System (Transit)

The Navy Navigation Satellite System (TRANSIT) has provided 100% system reliability since being declared operational October 11, 1968. TRANSIT continues to carry out its function of precise, reliable, all weather navigation for the United States Navy and nearly 80,000 worldwide commercial users. TRANSIT's utility has been expanded to provide precise positioning information to those in the fields of geodesy and doppler surveying. While TRANSIT's history is illustrious, its life is limited. The transition from TRANSIT as the Navy's satellite navigation system to NAVSTAR GPS is planned for the 1990' s, with the result that TRANSIT is now scheduled for phase out by the United States Navy in 1994. This paper (essentially an update of reference [1]) will show the current status and plans for TRANSIT, following a brief historical overview.     

Galileo系统对卫星导航系统的增强作用

介绍了正在建设的Galileo系统，从卫星导航系统的星座、完备性、通讯能力、求解载波相位整周模糊数能力以及对系统轨道漂移影响抑制能力五个方面入手，研究了Galileo系统对空间飞行器导航的增强作用。最后通过仿真研究．进一步分析了Galileo系统在空间飞行器导航应用中的增强作用。     

卫星导航陆基增强系统设备许可体系研究

陆基增强系统(GBAS)是支持飞机精密进近的下一代无线电导航设备。目前,在世界上安装GBAS和提供GBAS服务的机场越来越多。中国已经研制了首套卫星导航GBAS着陆系统,然而并没有通过相关设备的认证许可,未投入实际的运行使用。因此,本文在分析FAA和Eurocontrol对GBAS设备许可的基础上,提出了一套完整的卫星导航路基增强系统设备许可体系的方案,为进行设备的认证许可提供引导,使得整个地面子系统满足安装选址要求、地面和飞行测试对功能和性能的验证要求,保证地面设备子系统经过安装调试后能够达到理想的工作状态。设备许可体系在未来卫星导航技术的发展中发挥着广泛的指导作用,有利于设备的运行、发展和管理。     

NAVSAT: A Global Satellite Based Navigation System

The NAVSAT concept, developed by the European Space Agency, in close cooperation with the industries and user organizations has been conceived to fulfill the civilian user requirements for a better navigation capability and mobile communication needs in the future. In selecting the NAVSAT architecture, special care has been devoted to different satellite constellation alternatives in order to identify the most promising solution in terms of navigation performance and system cost. The paper describes the present NAVSAT baseline and status. This baseline while offering precise navigation performance comparable or better than GPS, cuts significantly the overall cost of a satellite navigation system. The particular constellation selected is also easing the set up of the integrated navigation-communications-search and rescue service.     

一种机载平台动态测姿精度检验方法

机载惯导平台目前只在实验室转台上进行过测试,实际动态情况下对较高姿态测量精度无法测试。本文针对这种情况,提出一种利用机载实况记录系统输出的测角数据、飞机和靶机位置数据等信息,对机载平台动态测姿精度进行检验的方法。     

Improvement of Satellite Tracking Accuracy Using Optical Observations

A method to improve satellite tracking accuracy is presented and discussed theoretically and experimentally in terms of two parts: correction for errors of the tracking system and correction of satellite orbit predictions. In the first part, it is concluded that the pointing error of the tracking system can be determined accurately using data from stellar observations, so that correction is possible with an accuracy of about 0.001°. In the second part, it is shown that apparent errors of satellite orbital elements can be deduced from the optical observation of one orbit, and one can track the satellite after the correction with high accuracy for several subsequent orbits. The accuracy is 0.1-0.2 mrad or better for satellites at 1000 km altitude when given orbit prediction accuracy is approximately 1°.     

Theoretical Bounds on Random Errors in Satellite Doppler Navigation

Analytic expressions of the random errors in a satellite Doppler navigation system are developed. The errors in the along-track and across-track coordinates are expressed as functions of the geometry (range and angle), pass-length, and signal-to-noise ratio (SNR). Such an analytic result becomes possible due to an explicit solution to a simplified rectilinear model of the satellite pass over a flat Earth. It is shown that the explicit solution performance in the presence of noise is identical to that of the iterative solution, used in the real navigation problem.